73 Million Trees in the Amazon: How Muvuca Seeding Restores Forest

First published November 18, 2017.

In 2017 Conservation International and its Brazilian partners launched what was then described as the largest tropical forest restoration effort ever attempted: bringing back about 73 million trees on roughly 30,000 hectares (about 74,000 acres) of cleared land in the Brazilian Amazon. Instead of planting seedlings one by one, the project relied on muvuca, a technique that scatters dense mixtures of native seeds directly onto the ground and lets the strongest plants take hold.

The target was never a count of trees already standing. It was a plan, and like most large restoration projects, its real test is what survives. By early 2023, Conservation International estimated that about 9.6 million trees were growing on 1,200 hectares restored with the muvuca method, around three times what the organisation first expected on that land. Here is how the project works, why the method matters, and what it can and cannot achieve.

Where the trees are going and why

The work focuses on the "arc of deforestation", the crescent along the southern and eastern edge of the Amazon where farming, ranching and roads have pushed deepest into the forest. It runs through states including Pará, Rondônia, Acre and Amazonas, and the project also targets the Xingu river basin, an area of Indigenous territories surrounded by soy fields and pasture.

The scale of the loss is the reason for urgency. Roughly a fifth of the Brazilian Amazon's original forest has already been cleared, most of it since the 1970s. Scientists warn that if deforestation goes much further, large parts of the rainforest could pass a tipping point and begin turning into drier, savanna-like landscapes, releasing huge amounts of carbon.

The project was designed to help Brazil meet its Paris Agreement pledge to restore 12 million hectares of forest by 2030, with work coordinated by Conservation International alongside Brazil's Ministry of Environment and other public and private partners.

How muvuca works

In Brazilian Portuguese, muvuca is an informal word for a crowd of people packed into a small space. As a restoration method, it means exactly that: a crowded mix of seeds from dozens or even hundreds of native species, often blended with sand and sometimes with seeds of fast-growing crops or legumes, sown thickly across prepared ground, either by hand or with ordinary farm machinery.

The idea is to imitate the way a forest regenerates naturally. Fast-growing pioneer species shoot up first, shading out grasses and improving the soil. Slower, longer-lived trees grow up beneath them and eventually take over. Because so many seeds are sown, the plants compete, and those best suited to that patch of ground survive.

The seeds for the Amazon project come from the Xingu Seed Network, a cooperative of about 400 collectors, many of them Indigenous people, smallholders and residents of rural settlements. Collecting and selling native seed gives these communities an income from standing forest, which adds a social benefit that a tree-nursery approach would not provide.

Why direct seeding can beat planting seedlings

Traditional reforestation raises seedlings in nurseries and plants them one at a time, which is slow and expensive. According to project lead Rodrigo Medeiros, quoted by Fast Company and Smithsonian, planting by hand typically produces around 160 plants per hectare, while muvuca can start with about 2,500 per hectare and reach far higher densities after a decade. Some early reports said 2,500 "species" per hectare; the figure refers to plants, not different species.

The method has other advantages:

• Lower cost. No nursery, less labour and the option of using farm machinery can cut costs considerably.
• Greater diversity. A broad seed mix produces a richer forest than rows of a few nursery species.
• Hardier plants. Trees that grow from seed where they fall develop deep roots from the start, which helps them cope with the long Amazonian dry season. A 2014 study by the FAO and Bioversity International, cited by Fast Company at the launch, found that more than 90 percent of native species sown this way germinated and could survive up to six months of drought without irrigation, though survival varies a great deal by site.

Conservation International's chief executive, M. Sanjayan, framed the project as a test of whether this approach could work across huge areas: "This is not a stunt. It is a carefully controlled experiment to literally figure out how to do tropical restoration at scale," he told Fast Company.

How the project has fared

Restoration is measured in survival, not in seeds. In a 2023 update, Conservation International estimated roughly 9.6 million trees growing on 1,200 hectares restored with muvuca, compared with the 3 million it had initially expected there. "This is a very good result, and it offers hope of overcoming the challenge of reducing restoration costs," said Miguel Moraes of Conservation International Brazil.

The organisation has also been open about obstacles: fires that burned some restored areas, the COVID-19 pandemic, early administrative problems and rising deforestation inside protected areas. By early 2023 it said almost 20 percent of the restoration target had been delivered, and the completion deadline had moved from 2023 to 2026, which shows how slow and hard real restoration is, even with a cheaper method.

What tree planting can and cannot do for the climate

Restoring forests is valuable, but it is not a substitute for protecting the forests that still stand. A widely cited 2017 study in the Proceedings of the National Academy of Sciences estimated that "natural climate solutions", a broad group of land-based actions including protecting forests, restoring them, and changing how farms and wetlands are managed, could provide about 37 percent of the cost-effective emissions cuts needed by 2030 to keep warming below 2°C. That figure covers all of those measures together, not reforestation or an end to deforestation alone.

A few points are worth keeping in mind when you read about any tree-planting headline:

• Old-growth rainforest stores far more carbon and supports far more wildlife than young regrowth, so preventing clearing comes first.
• A planting total says little until survival rates and forest cover are measured years later.
• Projects that pay and involve local people, as the seed network does, tend to last longer than those that do not.

The muvuca project matters less for its headline number than for what it tests: whether a cheaper, more natural method, supported by local communities, can bring degraded Amazon land back to life at a large scale. The early results suggest that it can, at least where the restored land is protected.

Sources: Conservation International: Amazon reforestation project; Conservation International: project update; Smithsonian Magazine; Fast Company; Inhabitat; Griscom et al., PNAS 2017: Natural climate solutions. Images via Depositphotos.